The wobble shaft, sometimes referred to as an universal shaft, is regarded as the weakest link in the drive mechanism of an orbital fluid pressure device. The function of the wobble shaft is to universally connect the Gerotor and the main shaft. In prior devices, the universal connection depended upon interfitting male and female spline teeth. These teeth provided universal relative movement therebetween in all directions other than in the direction that torque was being transmitted. They were not only weak mechanically but also were subject to an excessive amount of wear, which when it occurred affected the timing of the Gerotor.
Accordingly, it is an object of my invention to provide a wobble shaft which is mechanically strong and free from excessive wear.
Another object is the provision of universal connection means includng an internal polygonal socket configuration and an external polygonal head configuration interfittingly engaging each other for transmitting torque therebetween.
Another object is to provide for universal relative movement between the polygonal configurations in all direction other than in the direction that torque is being transmitted.
Another object of the provision whereby the external polygonal head configuration is defined by three substantially cylindrical surfaces.
Another object is whereby the interfitting polygonal configurations include at least flat wall means and contour wall means confrontingly engaging each other.
Another object is whereby the interfitting polygonal configurations upon the transmission of torque define at least a polygonally disposed line segment contact therebetween.
Another object is whereby the axis of the wobble shaft intersects the axis of the main shaft at an universal point and also intersects the axis of the rotor of the Gerotor at another universal point and whereby a line passing through an universal point and substantially perpendicular to the flat wall means of a polygonal configuration intersects said line segment contact.